occasion

1[countable]a particular time when something happenson this/that occasionI've met him on several occasions.I can remember very few occasions when he had to cancel because of poor health.They have been seen together on two separate occasions.On one occasion, she called me in the middle of the night.He used the occasion to announce further tax cuts.

2[countable]a special event, ceremony, or celebrationa great/memorable/happy occasionTurn every meal into a special occasion.They marked the occasion(= celebrated it) with an open-air concert.Their wedding turned out to be quite an occasion.He was presented with the watch on the occasion of his retirement.

3[singular]occasion (for something/doing something)a suitable time for somethingIt should have been an occasion for rejoicing, but she could not feel any real joy.I'll speak to him about it if the occasion arises(= if I get a chance).

4[uncountable,singular](formal)a reason or causeoccasion (to do something)I've had no occasion to visit him recently.She doesn't have much occasion to speak French in her new job.occasion (of/for something)Her death was the occasion of mass riots.I'm willing to go to court over this if the occasion arises(= if it becomes necessary).